No, I don't think nice round numbers like 20 or 100 years show a pattern. I like to think more in terms of generations: 15 to 30 years. I can't predict the future. Please take my 30 year time-line idea as numerology where similarly numbered years must resemble each other. It's broken into a decade each of boom-bust-war:
1890 boom "Klondike Gold Rush"
1900 bust "Panic of 1901"
1910 war WW1
1920 boom "Roaring"
1930 bust "Great Depression"
1940 war WW2
1950 boom "Golden Age" [1]
1960 bust [2]
1970 war Viet Nam
1980 boom "Long" [3]
1990 bust [4] [5]
2000 war Afghanistan, Iraq
2010 boom [6]
2020 bust [7]
2030 war [8]
Of course, there are booms, busts and wars occurring at anytime. And some parts of the world might feel like they are in the future and some in the past.